Proportional flow divider combiner



6 J. A. COMPTON ETAL 3,347,254

PROPORTIONAL FLOW DIVIDER COMBINER Filed Feb. 9, 1965 IN VEN TO R S JAMIIJ ,4. coM/ ra/v,

@ 2 JOHN a, 4405M ArraaM/a United States Patent Ofiice 3,347 ,254 Patented Oct. 17, 1967 3,347,254 PROPORTIONAL FLOW DIVIDER COMBINER James A. Compton, and John D. Allen, South Euclid, and

Ray G. Holt, Westlake, Ohio, assignors to Fawick Corporation, a corporation of Michigan Filed Feb. 9, 1965, Ser. No. 431,413 9 Claims. (Cl. 137101) This invention relates to a proportional flow divider/ combiner.

Prior to the present invention various valve arrangements have been proposed for use alternatively as a proportional flow divider, to divide a single inlet stream of hydraulic liquid into two separate branch outlet streams whose flow rates are kept proportional to one another at various inlet flow rates and pressures, and as a flow combiner, for similarly keeping proportional to one another and combining two separate inlet streams into a single outlet stream.

The present invention is directed to a novel and improved proportional flow divider/combiner which offers significant operating advantages over the previously proposed valve arrangements for this same general purpose.

A principal object of this invention is to provide a novel and improved proportional flow divider/ combiner which assumes its proper condition for either flow dividing or flow combining operation positively in response to fluid pressure and without depending upon a spring which may become defective.

Another object of this invention is to provide an improved proportional flow divider/ combiner of novel construction which avoids the trapping of fluid or air therein.

Another object of this invention is to provide an improved proportional flow divider/ combiner of novel construction which reduces its weight and size as compared with previous devices for this same general purpose.

Further objects and advantages of this invention will be apparent from the following detailed description of a' presently-preferred embodiment thereof, which is illustrated in the accompanying drawing.

In the drawing:

FIGURE 1 is a cross-section through a proportional flow divider/ combiner in accordance with the present invention; and V FIGURE 2 is a longitudinal section, partly in a vertical plane and the remainder in a horizontal plane, taken along the line 22 in FIGURE 1. 1

Referring to FIG. 1, the particular embodiment of the present invention shown therein comprises a housing or body 10 having a transverse cylindrical bore 11 which at one end communicates with an internally screwthreaded portion 12 adapted to receive a pipe (not shown). As shown in FIG. 2, the housing also defines first and second branch passages 13 and 14, respectively, which intersect the bore-11 at diametrically opposite locations.

The bore 11 snugly receives a cylindrical sleeve 15. At its right end in FIG. 1, this sleeve has a pair of slots 16 whose inner ends engage respective stop pins 17 carried by the housing. At its left end in FIG. 1, the sleeve is engaged by a coil spring 18. A snap ring 19 is seated on the housing 10 at the left end of bore 11. A washer 20, slidably mounted in the bore, engages the left end of spring 18. With this arrangement, spring 18 is engaged under compression between snap ring 19 and washer 20 at one end and sleeve at the other. Spring 18-biases' sleeve 15 to the position shown in FIG. 1, with the inner ends of its respective end slots 16 abutting against the stop pins 17. The sleeve has a pair of diametrically opposed openings 21 and 22 (FIG. 2) which register respectively with the upper ends of branch passages 13 and 14.

A piston 23 is slidably received in sleeve 15. At its right end in FIG. 1 this piston has an enlarged flange 24 slidably mounted in a counterbore 25 in the housing which intersects the right end of the bore 11 therein. At the intersection of this bore and counterbore the housing defines a transverse annular shoulder 26 for engagement by the piston flange 24 to limit the movement of the piston to the left. The piston is resiliently urged to the left by a coil spring 27, which is engaged under compression between the piston and a plug 28 threadedly mounted in the housing.

The interior of housing bore 11 and sleeve 15 up to the openings 21 and 22 constitutes a common passage in the present flow divider/ combiner.

The piston 23 and the respective openings 21, 2 constitute variable flow restrictions between this common passage and the two branch passages 13 and 14. The greater the flow the greater will be the fluid pressure acting on piston 23, and therefore the smaller will be the amount of flow restriction at 21, 22. However, under a wide range flow condition this flow restriction will produce a significant pressure differential between the common passage, on the one hand, and the two branch passages, on the other, depending upon the flow direction.

Both branch passages 13 and 14 extend down to a longitudinal bore 29 in housing 10. A throttling valve in the form of a hollow valve spool 30 is slidably mounted in bore 29. Midway along its length this valve spool is formed with an external annular groove 31, which communicates with a transverse passage 32 (FIG. 1) in the housing extending from the screw'threaded portion 12 at the left end of transverse bore 11. Valve spool 30 has an axial passage 33 therethrough and a plurality of radial passages 34 extending between the external groove 31 and the axial passage 33.

On opposite sides axially of the external groove 31 the valve spool 30 presents cylindrical land portions 35 and 36, respectively, which slidably, but sealingly, engage the wall of the housing bore 29 between the respective intersections of branch passages 13 and 14 with the bore.

To the left of its land portion 35 in FIG. 2, the valve spool presents a relatively long, annular, external groove 37 which provides fluid communication between the second branch passage 14 and an annular recess 38 in the housing. At the axially outward end of its external groove 37 the valve spool presents a cylindrical land portion 3%, which sealingly engages the housing bore 29 axially outward beyond recess 38 and projects part way across recess 38 to control the fluid fiow between the valve spool groove 37 and the housing recess 38. Recess 38 extends around, and intersects, the housing bore 29 and it communicates with a first branch port 39, to which an external pipe (not shown) may be connected.

Similarly, to the right of its land portion 36 in FIG. 2, valve spool 30 presents a relatively long, annular, external groove 40 which provides fluid communication between the other branch passage 13 and an annular recess 41 in the housing. At the axially outward end of its external groove 40 the valve spool presents a cylindrical land portion 30a, which sealingly engages the housing bore 29 axially outward beyond recess 41 and projects part way across recess 41 to control the fluid flow between the valve spool groove 40 and the housing recess 41. Recess 41 extends around, and intersects, the housing longitudinal housing bore 29. Valve spool 30 has a length less than the spacing between the inner ends of these plugs. When the valve spool is centered along bore 29, there is a first working space 45 between the inner end of plug 43 and the left end of the valve spool and a second working space 46 between the inner end of plug 44 and the right end of the valve spool.

The axial passage 33 in valve spool 30 is surrounded and intersected by an annular groove 47 which communicates with an internal longitudinal bore 43 in the valve spool leading to the first working space 45.

A similar annular groove 49 surrounding and intersecting the valve spool passage 33 communicates with an internal longitudinal valve spool bore 59 leading to the second working space 46.

A first pilot valve in the form of a piston 51 is slidably mounted in the spool valve passage 33, presenting cylindrical opposite end portions 52 and 53 which sealingly engage passage 33 on opposite axial sides of groove 47 when this pilot valve is in its axially outward position, as shown in FIG. 2. Between these end portions 52 and 53 the first pilot valve 51 has a relatively long, external, annular groove 54, which, in this position of pilot valve 51, provides fluid communication between groove 47 and a radial bore 55 in the valve spool which is connected to the first branch passage 13 in the housing. The valve spool carries a cross pin 56 which limits the axially outward movement of the first pilot valve 51 (to the right in FIG. 2). At its outer end portion 53, the first pilot valve 51 is exposed to the fluid pressure in the second working space 46, this end of the valve spool 30 having an end recess 57 for this purpose.

A second pilot valve in the form of a piston 58 is slidably mounted in the valve spool passage 33, presenting cylindrical opposite end portions 59 and 60' which sealingly engage passage 33 on opposite axial sides of groove 49 when this pilot valve is in its axially outward position, as shown in FIG. 2. Between these end portions 59 and 60 this second pilot valve has a relatively long, external, annular groove 61, which, in this position of pilot valve 58, provides fluid communication between groove 49 and a radial bore 62 in the valve spool which is connected to the second branch passage 14 in the housing. The valve spool carries a second cross pin 63 which limits the axially outward movement of the second pilot valve 58 (to the left in FIG. 2). At its outer end portion 60 the second pilot valve 58 is exposed to the fluid pressure in the first working chamber 45, this end of the valve spool 30 having an end recess 64 for this purpose.

The valve spool 30 carries a third cross pin 65 midway along its axial passage 33 which limits the axially inward movement of both pilot valves 51 and 58.

The spool valve bores 48 and 55, the portion of the axial spool valve passage 33 between them, and the portion of passage 33 between bore 55 and end recess 57 together constitute a first pilot passage in the valve spool 30. The first pilot valve 51 controls the fluid communication through this first pilot passage. When the first pilot valve 51 is in its axially outward position, as shown in FIG. 2, it connects the first working space 45 to the first branch passage 13 and blocks the first branch passage from the second working space 46. However, When the first pilot valve 51 is in its axially inward position, abutting against stop pin 65, it connects the first branch passage 13 to the second working space 46 by way of the radial valve spool bore 55, the axial valve spool passage 33 axially outward of the first pilot valve 51, and the end recess 57 in the valve spool, and also its outer end portion 53 blocks the fluid communication between the first branch passage and the first working space 45 by way of valve spool bore 48.

Similarly, the spool valve bores 54 and 62, the portion of the axial spool valve passage 33 between them, and the portion of passage 33 between bore 62 and end recess 4 64 together constitute a second pilot passage in the valve spool 30. The second pilot valve 58 controls the fluid communication through this second pilot passage. When the second pilot valve 58 is in its axially outward position, as shown in FIG. 2, it connects the second working space 46 to the second branch passage 14 and it blocks the second branch passage from the first working space 45. However, when the second pilot valve is in its axially inward position, abutting against stop pin 65, it connects the second branch passage 14 to the first Working space 45 by way of valve spool bore 62, the axial valve spool passage 33 axially outward from pilot valve 58, and the end recess 64 in the valve spool, and also its outer end portion 60 blocks the fluid communication between the second branch passage and the second working space 46 by way of valve spool bore 50.

Operation When the device is used as a flow divider, the direction of hydraulic liquid flow is from the common passage to the two branch passages 13 and 14. Hence, there is a fluid pressure drop from the common passage to each branch passage due to the flow-restricting action of piston 23 at the openings 21, 22 in sleeve 15.

The central space within the axial valve spool passage 33 between the inner ends of pilot valves 51 and 58 is at substantially the same fluid pressure as the common passage, due to the fluid communication between them which is provided by valve body passage 32 and groove 31 and transverse passages 34 in the valve spool. The fluid pressure in this central space is greater than the branch passage fluid pressure in the axial valve spool passage 33 at the intersections of the radial bores 55 and 62 therewith. Thus, there is an axially directed fluid pressure unbalance on each pilot valve 51 and 58 which forces the pilot valve axially outward to its position shown in FIG. 2. In this position, the first pilot valve 51 connects the first branch passage 13 to the first working space 45 by way of valve spool bores 55 and 48, and the outer end portion 53 of pilot valve 51 blocks the first branch passage 13 from the second working space 46. Also, in this position, the second pilot valve 58 connects the second branch passage 14 to the second working space 46 by way of valve spool bores 62 and 50, and the outer end portion 60 of pilot valve 58 blocks the second branch passage 14 from the first working space 45.

With the respective working spaces 45 and 46 at pilot pressures determined respectively by the fluid pressures in the branch passages 13 and 14, both of which are lower than the fluid pressure in the common passage, the fluid pressure differential acting on both pilot valves maintains them in their axially outward positions.

In the particular embodiment shown the valve arrangement is symmetrical as to both branch passage flows, so that the common inlet stream is divided into two equal branch streams. However, by appropriate design, a different ratio between the two branch stream flows may be provided.

The valve spool 30 automatically regulates the two branch streams as follows:

If the flow through the first branch passage 13 tends to increase over that through the second branch passage 14, the higher flow rate would produce a higher pressure drop from the common inlet passage to the first branch passage 13. Consequently, the fluid pressure in the first branch passage 13 would tend to decrease below that in the second branch passage 14. As a result, the pilot fluid pressure in the first working space 45 (which is in fluid communication with the first branch passage 13) is lower than that in the second working space 46 (which is in fluid communication with the second branch passage 14). The pilot fluid pressure differential acting endwise on valve spool 30 shifts it to the left in FIG. 2 to reduce the flow through the first branch passage 13 and to increase the flow through the second branch passage 14 until the respective fluid pressures and flow rates in the two branch passages are equalized.

The reverse action takes place if the flow through the second branch passage 14 tends to increase over that through the first branch passage 13.

When the device is used as a flow combiner, the direction of hydraulic liquid flow is from the branch passages 13 and 14 to the common passage. Due to the pressure drop across each opening 21 or 22, the fluid pressure in each branch passage will be higher than the fluid pressure in the common passage. Due to the resulting axially inwardly directed fluid pressure differential acting on each of the pilot valves 51 and 58, both pilot valves move inward against the central stop pin 65.

In its inward position, the first pilot valve 51 has its outer end portion 53 blocking the first branch passage 13 from the first working space 45, and the first branch passage 13 is connected to the second working space 46 through the radial valve spool bore 55 and the axial passage 33 and the end recess 57 in the valve spool axially outward beyond the inwardly-positioned pilot valve 51. In its inward position, the second pilot valve 58 has its outer end portion 60 blocking the second branch passage 14 from the second working space 46, and the second branch passage 14 is connected to the first working space 45 through the radial valve spool bore 62 and the axial passage 33 and the end recess 64 in the valvespool axially outward beyond the inwardly-positioned pilot valve 58.

The valve spool 30 automatically regulates the respective flows through the branch passages into the common passage as follows:

If the flow through the first branch passage 13 tends to increase over that through the second branch passage 14, then the fluid pressure in the first branch passage 13 (ahead of the flow restriction at opening 21) will tend to increase over that in the second branch passage 14 (ahead of the flow restriction at opening 22). Consequently, the pilot fluid pressure in the second working space 46 (which is now in fluid communication with the first branch passage 13) will increase over that in the first working space 45 (which is now in fluid communica tion with the second branch passage 14). The difierence in the respective opposing pilot fluid pressures in these working spaces, acting endwise on valve spool 30, shifts the latter to the left to reduce the flow through the first branch passage 13 and increase the flow through the second branch passage 14 until the respective fluid pressures and How rates in the two branch passages are equalized.

The reverse action takes place if the flow through the second branch passage 14 tends to increase over that through the first branch passage 13.

With the illustrated construction of the present invention, the pilot valves 51 and 58 assume their correct positions within the valve spool in a positive fashion in response to the fluid pressure differential acting on them, either for flow divider or flow combiner operation. No springs are required for their positioning under either type of operation. Because the pilot valves are within the valve spool the overall size and weight of the flow divider/ combiner are minimized. In the operation of the invention, there is no possibility of trapping air or liquid, which might interfere with its proper performance.

While a presently-preferred embodiment of this invention has been described in detail and illustrated in the accompanying drawing, it is to be understood that the invention is susceptible of other structural embodiments and that various modifications, omissions and refinements which depart from the disclosedembodiment may be adopted without departing from the spirit and scope of this invention. For example, the pilot valves maybe in the valve body instead of in the valve spool, if desired.

We claim:

1. A proportional flow divider/combiner comprising:

flow restriction means between means defining a common passage and first and second separate branch passages connected to said common passage;

throttling valve means controlling the respective fluid flows through said branch passages, said throttling valve means being displaceable in one direction to increase the fluid flow through one of said branch passages and decrease the fluid flow through the other of said branch passages, said throttling valve means being displaceable in the opposite direction to decrease the fluid flow through said one branch passage and increase the fluid flow through said other branch passage;

flow restriction means between said common passage and each branch passage;

means defining a first working space for pilot fluid pressure acting against said throttling valve means to apply a first pilot fluid force thereon in said one direction;

means defining a second working space for pilot fluid pressure acting against said throttling valve means to apply a second pilot fluid force thereon in said opposite direction;

said throttling valve means being displaceable, in response to an unbalance of the oppositely directed pilot fluid forces in said first and second Working spaces, in a direction to eliminate: said unbalance by changing the respective fluid filows through said branch passages;

and a pair of pilot valves respectively connected between said branch passages and said working spaces, said pilot valves being fluid pressure unbalanced, when the direction of fluid flow is from said-common passage to said branch passages, to connect said first branch passage to said first working space and to connect said second branch passage to said second working space, said pilot valves being fluid pressure unbalanced, when the direction of fluid flow is from said branch passages to said common passage, to reverse the connections of said branch passages to said working spaces.

2. A proportional flow divider/combiner comprising:

housing means having a common passage and separate first and second branch passages connected to said common passage;

throttling valve means in said housing controlling the respective fluid flows through said branch passages, said throttling valve means being displaceable in one direction in said housing means to increase the fluid flow through one of said branch passages and decrease the fluid flow through the other of said branch passages, said throttling valve means being displaceable in the opposite direction to decrease the fluid flow through said one branch passage and increase the fluid flow through said other branch passage;

said common passage and each branch passage;

means defining a first working space for pilot fluid pressure in said housing means acting against said throttling valve means to apply a first pilot fluid force thereon in said one direction;

means defining a second working space for pilot fluid pressure in said housing means acting against said throttling valve means to apply a second pilot fluid force thereon in said opposite direction;

said throttling valve means being displaceable, in response to an unbalance of the oppositely directed pilot fluid forces in said first and second working spaces, in a direction to eliminate said unbalance by changing the respective fluid flows through said branch passages;

first and second pilot valves respectively connected be tween said branch passages and said working spaces to control the fluid communication therebetween, said first pilot valve in a first position thereof con- 7 necting said first branch passage to said first working space, said second pilot valve in a first position thereof connecting said second branch passage to said second working space, said pilot valves in a second position thereof reversing the connections between said branch passages and said working spaces; and means for pressure unbalancing both said pilot valves to said first position thereof in response to fluid flow from said common passage to said branch passages and for pressure unbalancing both said pilot valves to said second position thereof in response to fluid flow from said branch passages to said common passage.

3. A proportional flow divider/combiner comprising:

housing means having a bore therein, a common passage, and separate first and second branch passages connected to said common passage and intersecting said bore at spaced locations thereon;

a valve spool slidable in said bore to control the respective fluid flows through said branch passages, said valve spool being displaceable in one direction along said bore to increase the fluid flow through said first branch passage and decrease the fluid flow through said second branch passage, said valve spool being displaceable in the opposite direction along said bore to decrease the fluid flow through said first branch passage and increase the fluid flow through said second branch passage;

variable flow restriction means in said housing means between said common passage and each branch passage ahead of said valve spool, said flow restriction means providing flow restricting orifices between said common passage and said branch passages whose size varies with the fluid pressure in said common passage;

means defining a first working space for pilot fluid pressure in said housing means acting against said valve spool to apply a first pilot fluid force thereon in said one direction;

means defining a second working space for pilot fluid pressure in said housing means acting against said valve spool to apply a second pilot fluid force thereon in said opposite direction;

said valve spool being displaceable, in response to an unbalance of the oppositely directed pilot fluid forces in said first and second working spaces, in a direction along said bore to eliminate said unbalance by changing the respective fluid flows through said branch passages;

first and second pilot valves respectively connected between said branch passages and said working spaces to control the fluid connections therebetween, said first pilot valve in a first position thereof connecting said first branch passage to said first working space, said second pilot valve in a first position thereof connecting said second branch passage to said second working space, said pilot valves in a second position thereof reversing the connections between said branch passages and said working spaces;

and means subjecting each of said pilot valves to a fluid force determined by the fluid pressure differential between said common passage and the respective branch pass-age so as to position said pilot valves in said first position thereof when the fluid pressure in said common passage exceeds that in said branch passages and to position said pilot valves in said second position thereof when the fluid pressure in said branch passages exceeds that in said common passage.

4. A proportional flow divider/combiner comprising:

a housing having a bore therein, a common passage,

and first and second separate branch passages connected to said common passage and intersecting said bore at spaced locations thereon;

a valve spool slidable in said bore and operable by its position along the bore to control the respective fluid flows through said branch passages, said valve spool being displaceable in one direction along said bore to increase the fluid flow through said first branch passage and decrease the fluid flow through said second branch passage, said valve spool being displace able in the opposite direction along said bore to decrease the fluid flow through said first branch passage and increase the fluid flow through said second branch passage;

flow restriction means in said housing between said common passage and each branch passage ahead of said valve spool;

means defining a first working space in said housing at one end of said valve spool for pilot fluid pressure acting against said valve spool to apply a first pilot fluid force thereon in said one direction;

means defining a second working space in said housing at the opposite end of said valve spool for pilot fluid pressure acting against said valve spool to apply a second pilot fluid force thereon in said opposite di rection;

said valve spool having first and second pilot passages therein for connecting said branch passages to said working spaces;

and first and second pilot valves respectively controlling the fluid connections between said pilot passages and said working spaces;

said first pilot valve in a first position thereof connecting said first branch passage to said first working space through said first pilot passage, said second pilot valve in a first position thereof connecting said second branch passage to said second working space through said second pilot passage;

said first pilot valve in a second position thereof connecting said first branch passage to said second working space through said first pilot passage, said second pilot valve in a second position thereof connecting said second branch passage to said first working space through said second pilot passage;

said pilot valves being pressure unbalanced to said first positions when the direction of fluid flow is from said common passage to said branch passages, and said pilot valves being pressure unbalanced to said second positions when the direction of fluid flow is from said branch passages to said common passage.

5. A proportional flow divider/combiner comprising:

means defining a common passage and first and second separate branch passages connected to said common passage;

throttling valve means controlling the respective fluid flows through said branch passages, said throttling valve means being displaceable in one direction to increase the fluid flow through one of said branch passages and decrease the fluid flow through the other of said branch passages, said throttling valve means being displaceable in the opposite direction to decrease the fluid flow through said one branch passage and increase the fluid flow through said other branch passage;

flow restriction means between said common passage and each branch passage;

means defining a first working space for pilot fluid pressure acting against said throttling valve means to apply a first pilot fluid force thereon in said one direction;

means defining a second working space for pilot fluid pressure acting against said throttling valve means to apply a second pilot fluid force thereon in said opposite direction;

said throttling valve means being displaceable, in response to an unbalance of the oppositely directed pilot fluid forces in said first and second working spaces, in a direction to eliminate said unbalance by changing the respective fluid flows through said branch passages;

and pilot valve means carried by said throttling valve means for selectively connecting said branch passages individually to said working spaces, said pilot valve means being fluid pressure unbalanced, when the direction of fluid flow is from said common passage to said branch passages, to connect said first branch passage to said first Working space and to connect said second branch passage to said second working space, said pilot valve means being fluid pressure unbalanced, when the direction of fluid flow is from said branch passages to said common passage, to reverse the connections of said branch passages to said working spaces.

6, A proportional flow divider/combiner comprising:

housing means having a common passage and a pair of separate branch passages connected to said common passage;

throttling valve means in said housing controlling the respective fluid flows through said branch passages, said throttling valve means being displaceable in one direction in said housing means to increase the fluid flow through one of said branch passages and decrease the fluid flow through the other of said branch passages, said throttling valve means being displaceable in the opposite direction to decrease the fluid flow through said one branch passage and increase the fluid flow through said other branch passage;

flow restriction means between said common passage and each branch passage;

means defining a first working space for pilot fluid pressure in said housing means acting against said throttling valve means to apply a first pilot fluid force thereon in said one direction;

means defininig a second working space for pilot fluid pressure in said housing means acting against said throttling valve means to apply a second pilot fluid force thereon in said opposite direction;

said throttling valve means having a pair of separate pilot passages therein providing fluid communication respectively between said branch passages and said working spaces;

said throttling valve means being displaceable, in re sponse to an unbalance of the oppositely directed pilot fluid forces in said first and second working spaces, in a direction to eliminate said unbalance by changing the respective fluid flows through said branch passages;

a pair of pilot valves respectively positioned in said pilot passages in said throttling valve means to control the respective fluid connections therethrough between said branch passages and said working spaces, one of said pilot valves in a first position thereof connecting one of said branch passages to said first working space, the other of said pilot valves in a first position thereof connecting the other of said branch passages to said second Working space, said pilot valves in a second position thereof reversing the connections between said branch passages and said working spaces;

and means for pressure unbalancing said pilot valves to said first position thereof in response to fluid flow from said common passage to said branch passages and for pressure unbalancing said pilot valves to said second position thereof in response to fluid flow from said branch passages to said common passage.

7. A proportional flow divider/combiner comprising:

housing means having a bore therein, a common passage, and a pair of separate branch passages connected to said common passage and intersecting said bore at spaced locations thereon;

a valve spool slidable in said bore to control the respective fluid flow through said branch passages, said valve spool being displaceable in one direction along said bore to increase the fluid flow through one of said branch passages and decrease the fluid flow through the other of said branch passages, said valve spool being displaceable in the opposite direction along said bore to decrease the fluid flow through said one branch pasage and increase the fluid flow through said other branch passage;

flow restriction means in said housing means between said common passage and each branch passage ahead of said valve spool, said flow restriction means defining flow restricting orifices between said common passage and said branch passages whose sizes vary with the fluid pressure in said common passage;

means defining a first working space for pilot fluid pressure in said housing means acting against said valve spool to apply a first pilot fluid force thereon in said one direction;

means defining a second working space for pilot fluid pressure in said housing means acting against said valve spool to apply a second pilot fluid force thereon in said opposite direction;

- said valve spool having a pair of separate pilot passages thereon providing fluid communication respectively between said branch passages and said working spaces;

said valve spool being displaceable, in response to an unbalance of the oppositely directed pilot fluid forces in said first and second working spaces, in a direction along said bore to eliminate said unbalance by changing the respective fluid flows through said branch passages;

a pair of pilot valves respectively positioned in said pilot passages in the valve spool to control the fluid connections therethrough between said branch passages and said working spaces, one of said pilot valves in a first position thereof connecting one of said branch passages to said first Working space, the other of said pilot valves in a first postiion thereof connect ing the other of said branch passages to said second Working space, said pilot valves in a second position thereof reversing the connections between said branch passages and said working spaces;

and means subjecting each of said pilot valves to a fluid force determined by the fluid pressure difierential between said common passage and a respective branch passage so as to position said pilot valves in said first position thereof when the fluid pressure in said common passage exceeds that in said branch passages and to position said pilot valves in said second position thereof when the fluid pressure in said branch passages exceeds that in said common passage.

8. A proportional flow divider/combiner comprising:

a housing having a bore therein, a common passage, and first and second separate branch passages connected to said common pasage and intersecting said bore at spaced locations thereon;

a valve spool slidable in said bore and operable by its position along the bore to control the respective fluid flows through said branch passagse, asid valve spool being displaceable in one direction along said bore to increase the fluid flow through one of said branch passages and decrease the fluid flow through the other of said branch passages, said valve spool being displaceable in the opposite direction along said bore to decrease the fluid flow through said one branch passage and increase the fluid flow through said other branch passage;

flow restriction means in said housing between said common passage and each branch passage ahead of said valve spool;

means defininig a first working space in said housing at one end of said valve spool for pilot fluid pressure acting against said valve spool to apply a first pilot fluid force thereon in one direction;

means defining a second working space in said housing said valve spool having a longitudinal passage therethrough, a first pair of bores intersecting said longitudinal passage at spaced locations therealong and connected respectively to said first working space and said first branch passage, a first pilot valve slidable in said longitudinal passage at the intersections of said first pair of bores therewith, said first pilot valve in an outward position thereof along said longitudinal passage connecting said first branch passage to said first working space through said first pair of bores and said longitudinal passage and blocking said first branch passage from said second working space, said pilot valve in an inward positon thereof along said longitudinal passage blocking fluid flow between said first pair of bores and connecting said first branch passage to said second working space through one of said first pair of bores and said longitudinal passage;

said valve spool having a second pair of bores intersecting said longitudinal passage at spaced locations therealong and connected respectively to said second working space and said second branch passage, a secong pilot valve slidable in said longitudinal passage at the intersections of said second pair of bores therewith, said second pilot valve in an outward position and passage means extending between said common 9. claim 8, wherein there are provided stop members on said spool for limiting the outward and inward movements of passage and said longitudinal passage in the valve spool between said first and second pilot valves therein whereby both pilot valves are pressure unbalanced to their outward positions when the direction of fluid flow is from said common passage to said branch passages and both pilot valves are pressure unbalanced to their inward positions when the direction of fluid flow is from said branch passages to said common passage.

A proportional flow divider/ combiner according to the respective pilot valves along said longitudinal passage.

thereof along said longitudinal passage connecting said second branch passage to said second working space through said second pair of bores and said References Cited UNITED STATES PATENTS 2,365,095 12/1944 Miller et al. 137l01 2,413,896 1/1947 Trautman et al 137l01 2,460,774 2/1949 Trautman 137-101 2,956,577 10/1960 Kirkham 137-l0l WILLIAM F. ODEA, Primary Examiner.

D. J. ZOBKIW, Assistant Examiner. 

1. A PROPORTIONAL FLOW DIVIDER/COMBINER COMPRISING: MEANS DEFINING A COMMON PASSAGE AND FIRST AND SECOND SEPARATE BRANCH PASSAGES CONNECTED TO SAID COMMON PASSAGE; THROTTLING VALVE MEANS CONTROLLING THE RESPECTIVE FLUID FLOWS THROUGH SAID BRANCH PASSAGES, SAID THROTTLING VALVE MEANS BEING DISPLACEABLE IN ONE DIRECTION TO INCREASE THE FLUID FLOW THROUGH ONE OF SAID BRANCH PASSAGES AND DECREASE THE FLUID FLOW THROUGH THE OTHER OF SAID BRANCH PASSAGES, SAID THROTTLING VALVE MEANS BEING DISPLACEABLE IN THE OPPOSITE DIRECTION TO DECREASE THE FLUID FLOW THROUGH SAID ONE BRANCH PASSAGE AND INCREASE THE FLUID FLOW THROUGH SAID OTHER BRANCH PASSAGE; FLOW RESTRICTION MEANS BETWEEN SAID COMMON PASSAGE AND EACH BRANCH PASSAGE; MEANS DEFINING A FIRST WORKING SPACE FOR PILOT FLUID PRESSURE ACTING AGAINST SAID THROTTLING VALVE MEANS TO APPLY A FIRST PILOT FLUID FORCE THEREON IN SAID ONE DIRECTION; MEANS DEFINING A SECOND WORKING SPACE FOR PILOT FLUID PRESSURE ACTING AGAINST SAID THROTTLING VALVE MEANS TO APPLY A SECOND PILOT FLUID FORCE THEREON IN SAID OPPOSITE DIRECTION; SAID THROTTLING VALVE MEANS BEING DISPLACEABLE, IN RESPONSE TO AN UNBALANCE OF THE OPPOSITELY DIRECTED PILOT FLUID FORCES IN SAID FIRST AND SECOND WORKING SPACES, IN A DIRECTION TO ELIMINATE SAID UNBALANCE BY CHANGING THE RESPECTIVE FLUID FLOWS THROUGH SAID BRANCH PASSAGES; AND A PAIR OF PILOT VALVES RESPECTIVELY CONNECTED BETWEEN SAID BRANCH PASSAGES AND SAID WORKING SPACES, SAID PILOT VALVES BEING FLUID PRESSURE UNBALANCED, WHEN THE DIRECTION OF FLUID FLOW IS FROM SAID COMMON PASSAGE TO SAID BRANCH PASSAGES, TO CONNECT SAID FIRST BRANCH PASSAGE TO SAID FIRST WORKING SPACE AND TO CONNECT SAID SECOND BRANCH PASSAGE TO SAID SECOND WORKING SPACE, SAID PILOT VALVE BEING FLUID PRESSURE UNBALANCED, WHEN THE DIRECTION OF FLUID FLOW IS FROM SAID BRANCH PASSAGES TO SAID COMMON PASSAGE, TO REVERSE THE CONNECTIONS OF SAID BRANCH PASSAGES TO SAID WORKING SPACES. 